Fluid paste of anthraquinone compounds



Pastas Jur 2, 11935 PASTE F PATE T oFncEY' mnnaoumonn coMroUNns' ADonald G., Rogers, Hamburg, N. Y., aaaignor to' National Aniline and'Chemical Company, Inc" New York, N. Y., a corporation of New York' .NoDrawing. Application July 19, 1030, Serial No. 469,259-- v v 26 Claims.

This invention relates to fluid pastes-cinnthraquinone compounds, andmore particularly to highly concentrated aqueous fluid pastes ofanthraquinohe compounds (that is, suspensions of the anthraquinonecompounds in water which have high concentrations of the anthraguinonecompound),- and to.-prccesses of producing the same. The invention alsorelates to highly concentrated filter-cakes and equivalent masses ofanthraquinone compounds andprocesses ofpro P ducing them.

In the manufacture of metal-free a'nthraquinone compounds, bothdyestuffsand intermediates, 7 the compound is often produced in the form of aprecipitate in. suspension in a mother liquor from whichdt is separatedby filtration, and the resulting. filter-cake is washed free from themother liquor and agitated with water to'disintegrate it and forma fluidsuspension or so-called paste. When produced ii -this manner, the fluidI paste has a concentration of organic compound of about 15 to'30percent. by weight.

These pastes have the evident disadvantage e that they contain a verylarge proportion of an inert ingredient, water (usually 70 to 85percent. by weight), whichadds greatly tothe cost of containers andtransportation, and, therefore, to the ultimate cost oftheproduct to theconsumer, on the basisof content. of active material.

Various proposals have been-advanced having for their object a reductionor elimination of the; water content of the'ipastjes, and the productionor a powder or. of almoreconcentrated paste. While incertain instancesthe results ofsuch .41; proposals have'been satisfactory, in general thesolution of thedimcultyintroduces factors which farethemselv'esundesirable, andofls'et the bene- -flts derived. j' 3 a" Inthe case of"alizarine (1.2 -dlhydrOUanthra D ducedas a 20 per cent. -aqeous paste by filtering a suspen'slonrof alizarinein dilute acid,washing the filter-cake with',wa.ter,-'blowing air the filter-cake toremove-water. and agitating 1' the resulting filter-cake, whichcontainsabout "to 25 per :cent. by weight of dyestuihzwith the.requiredamount'o'fwater to form the 20 per cent. fluid pas e. [it-hasto'reuuce the water content "or the nlter 'cak e hy blowing air throughit for every merely increases the strength of the to,

about28 per cent-by-Weight of-dyestuff, which hardly compensatesfor the.added of the extended aeration. It also'has een proposed to quinone) forexample, which --is generally pro- This, however,

101.8-6) insoluble thickening agents, and evaporate the, mixture,whereby solid-lumpy preparations are produced which can beredlspersedwith water for use, and which contain a high percentage ofalizarine. But such preparations are notjacceptable for the manufactureof certain products such as lakes, owing toth'e presence of theinsoluble thickening agent in the suspension formed upon redispersion ofthe aliz arine. 7 An object of'the present inventioniis to prpduce' l0.fluid suspensions, or pastes, of water-insoluble anthraquinone compoundswhich contain more than 30 per cent. by weight of the anthraquinonecompound, which aregpreierablynon-drying, and which are relatively freefrom insoluble thickeni5 ingagents.

Other. objects of theinvention. are .to provide a process wherebyillterecakes, and equivalent masses of water-insoluble metal-:freeanthraquin'one compounds may be-produced which con- 20 .tain water and agreater amount of waterln-- soluble anthraquinone compound than thefiltercakes obtainable by filtration of a suspension or theanthraquinone compound in dilute acid, and to provide a', process forthe production of fluid e5v aqueous suspensions having highconcentration of the 'anthraquinone compound from said ,fllter-'cakesormasses. j

. Additional objects of-the invention are to-pro-,-

duce aqueous suspensions of water-insoluble sin-T80;

. thraquinone dyestuffs-which con'tain'i'nore than 40 per cent. byweight of the dvestulf, and are-'rela; tively freefrom insolublethickening agents; and to provide -a process suspensions. J

- A further object or the invention is to provide, .'a process fol-theproduction of'a stab1e,'.thin, 4

:Ifluid, aqueous aispension ofalizarine which contains more than 30 percent. of ali'zarine-by weight.

. Other obiects'of the invention 'willinpart' heal! obvious and will inpart appear hereinafter.

The invention accordingly comprises thenew; productsas well as theseveral steps and-the rela-y vtion of one or more of such stepswith-respect- I to others thereof employed inthw'preparatlon of,

such products whichwill be exhmplified in the products hereinafterdisclosed. 3 I

, the invention will be indicated. in'therdingtovthepresent-jinventlom'composi- Mons water-insoluble anthraqulnoneoompo'undsmay be which contain great-' e'r percentages by "weight ot:the anthraquinone compounds than are ordinarily present inthe" m n mu-onwai6,

forthe-production of such.

pensions of the anthraquinone compounds in dilute acid, by agitating aliquid containing mass of acid, with'water' and preferably I dispersingagent, if necessary),

a water-insoluble anthraquinone compound, resulting from the mechanicalseparation of a suspension'of the anthraquinone compound in dilute witha relatively small amount of a dispersing agent, to produce a suspensionor slurry of the anthraquinone compound,and mechanically separating thesuspended compound from the liquid. Furthermore, according to thepresent invention, thin, fluid, aqueous suspensions of the may beprepared which also contain high concentrations of anthraquinonecompounds by reslurrymg the mass .of separated compound, for example, byagitation of said mass of separated compound (with the further additionof a small amount of dispersing agent, if necessary). I have foundthatthe product separation of the suspended compound from the liquid oftheaqueous suspension contains the anthraquinone compound in a muchhigher-concentration than the mass employed as the starting material;and also, that said product, when agitated (with the addition of a smallamount of forms a thin, mo-

; bile, fluid. suspension which also contains the an-.

of procedure, a

' render the subiecting it to stirring,

thraquinone compound in a relatively high concentration. I have found,furthermore, that the resulting thin, mobile, fluid suspension,containing the anthraquinone compound in a relatively highconcentration, can be still further concentrated by a repetition of theseparating and-res'lurrying operations. a

Moreover, according to the present invention, relatively non-dryinghighly concentrated suspensions of anthraquinone compounds may beproduced by' incorporating a hygroscopic sub-' stance into saidsuspensions.

In addition, according to the present invention,

aqueous suspensions of water-insoluble anthraquinone compounds areproduced containing more than 30 per cent. by weight of theanthraquinone compound and a small amount of a protective colloid as astabilizing agent. I have'found that such aqueous suspensions ofwater-insoluble anthraquinone compounds may be permitted to stand for aconsiderable length of time without settling of the suspended materialto a hard mass, and furthermore that any ofthe anthraquinone compoundwhich settles may be readily again dispersed merely by stirring themass.

In carrying out theprocess of the present inyention, in accordance witha preferred method filter-cake of a water-insoluble anthraquinonecompound, as forexample, a filter-cake of an alizarine dyestufl obtainedby the flltrationvof a suspension of the dyestufl in a dilute acidfollowed by washing of the press-cake with water, may be subjected tostirrinmprcfer ably with the addition of an agent which iscapableofthinningordispersingthemass dreducing its viscosity (and, ifnecessary, the

- addition of a small amount of water sufilcient to mass agitable) andthe resulting slurry may be filtered to remove the, water and.

to form a concentrated, thin, fluid susfin'sio'm'or paste, of theanthraquinone compound, the highly concentrated filter-cake may bereslurried by with the addition of a small amount of a agent, ifnecessary. A filter-cake having astill higher concentration of theanthraquinone compo md'm'ay be obtained by a reiiltrationoftheanthraquinone compounds which results from the trate, otherwisedeflocculating or dispersing resulting suspension; and a correspondinglymore suspension may. be produced from the resulting filter-cake by arepetition of the reslurryins operation.

Among the agents which may be added to the fllter-caketo aid in reducingthe viscosity and in producing deflocculation or dispersion, alkalinematerials, such as the caustic alkalis, ammonium hydroxide, etc, may beparticularly mentioned. These may be employed alone or in conjunctionwithother deflocculating or. dispersing agents, as for example,colloiding agents, such as alkylnaphthalene sulfonic acids and relatedsubstances, formaldelrvde condensation products of alkyl-naphthalenesulfonic acids and related substances, Turkey-red oil, saponin, soaps oithe higher saturated or unsaturated fatty acids or resin acids, etc.Substances which are both alkaline materials and colloiding agents mayalso be employed to advantage; for example, diethanolamine,triethanolamine, technical mixtures of alkanol amines, etc.

The amount ofdispersin or deflocculating agent employed should besuflicient to reduce the viscosity of the filter-cake to an extent suchthat it can be fl1tered,but so great an amount should not be used thatexcessive dispersio is obtained resulting in passage of the materialthrough the fllter without leaving a filter-cake. In general, the amountshould be such that only a relatively small or minor portion of thedispersed anthraquinone compound, if any, passes into the illthe yieldof concentrated filtercake and/or paste-obtained is uneconomicallydecreased. 1

Any suitable alkaline material may be employed to reduce the viscosityofthe filter-cake and render it more-dispersible, 'as for example, sodiumhydroxide, sodium carbonate, potassium hydroxide, potassium carbonate,borax, ammonium hydroxide,

disodium phosphate, methyl amine, etc.

An alkaline compound of an alkali metal or of ammonia is preferred,however. The alkaline material preferably may be employed in an amountsuflicient to form a of the anthraquinone compound; A large excess ofthe alkaline material is preferably avoided. since it tends to causesettling 'out of the comthin, fluid dispersion pounduponstanding;asmallexcessmaybeused,

yhowever. Inpractice, amounts of alkali may, be, used as high as about 3per cent. by weight or the anthraquinone compound in pendin up nemploying an alkaline compound, such as an alkali-metal hydroxide orammonium hydroxide,

the filter-cake, y dewith a dihydroxyanthraquinone compound, however, itis preferable that the amount employed be less than that required toproduce ciable amount of the corresponding salt of thedihydroxyanthraquinone compound, which can be readily detected bycolorimetric tests. In reslurrying fromthe filtration of a slurry.produced with the aid of an alkaline, material, for the production of aconcentrated suspension or so-called paste, additional alkaline materialbe added, inasmuch as thefllter-cake disperses. 'in some cases merelyupon being stirred.

The-employment of a colloiding agentwin conjunction with an alkalinematerial is especially advantageous in those cases where the alkaline anapprethe compound treated. when a concentrated filter-cake, resultingfrequently need not material by itself does not produce a satisfactory Idispersion of the filter-cake, as for example, in the case of ananthraquinone paste obtained by filtering a suspension .of anthraquinonein dilute employed will vary depending upon the compound being treatedand the other conditions of the treatment. Amounts varying from aboutonefourth to. about five percent. of the weight of the anthraquinonecompound in the filter-cakemay be advantageously employed in practice,although the invention is not limited to such amounts.

The highly concentrated pastes or suspensions resulting from the processmay settle to some extent upon standing for a considerable length oftime, particularly when dispersion has been effected with the aid of analkaline material alone. Such pastes or suspensions may be renderedcompartively non-settling by mixing with the paste a small amount of aprotective colloid as a stabilizing agent; for example, 0.1 to 2 percent. of the I weight of the anthraquinonecompound'in the I paste.

The stabilizing agent, which, when employed, may be incorporated at anysuitable stage of the process (for example, during the formation of thepaste or suspension, or after its formation), may be any suitableprotective colloidal material; as for example, sulflte cellulose wasteliquor, sulfonated castor oil, alkylnaphthalene sulfonic acids,alkylnaphthalene-formaldehyde-sulfuric acid'condensation products, alkylcellulose, aryl esters of phosphoric acid, benzylarylamine sulfonicacids, agar-agar, pectin, bentonite or other colloidal clay,-glue, etc.

If desired, hygroscopic substances, particularly high-boiling, inert,organic liquidhygroscopic substances, also may be incorporated into thepastes or suspensions in order to increase their keeping qualities andprevent undue loss of -mois turewhen the containers in which theproducts are stored by the consumer are left open to the ,atmosphere forlong periods of time. Hygroscopic' substances especially suitable forthe purpose are, for example, diethylene glycol, glycerine,

glycol, etc.

As illustrative embodiments of amanner in which the invention may becarried into practice, and of the products produced,the followingexamples are presented. The parts are by weight.

Example 1.-833 parts of anv Alizarine NAC filter-cake (containing about24 per cent. of dyestufl and .obtained by filtering oil alizarine from a.suspension thereof in dilute sulfuric acid followed by washing thefilter-cake with water until substantially free from acid) is agitatedwith about 165'parts of water and about 2 parts of 30 per. cent. sodiumhydroxide solution until a fluid suspension is'obtained. The resultingsuspension is filtered in a filter press of the ordinary plate. andframe type containing the usual square or twill weave cottonfilterciothyand air ,is blown through the press cake until substantially nomore water can ,be removed. About 466 parts of a press-cake is obtainedwhich contains about 42 per cent. by weight of dyestufi. The resultingpress-cake is stirred, and if the lumps donot disintegrateand the massdoes not become thin and mobile, sodium hydroxide solution is added atintervals in v small portionsuntil the press-cake scribed, other.

paste, containing 200 parts of dyestufi and prepared for example in themanner described in Example 1, is filtered on a filter press of theordinary type, and the press-cake is blown with air.

About 250 parts of a press-cake is obtained which contains about 70 percent. by weight of dyestufi'. By slurrying the resulting press-cake withabout 20 parts of water and a small amount of alkali (about part of 30per cent. aqueous sodium hydroxide) in the manner described in Example1, a fluid paste is obtained containingabout 65 per cent. by weight ofdyestufi. Example 3.500 parts of a 40 per cent. Alizarine NAC pasteprepared in the manner described in Example 1, is agitated with about ,6parts of a neutralized concentrated sulfite cellulose waste liquor. Theresulting product is a thin, mobile, fluid paste, which contains about'40'per cent. of alizarine, which settles only to a small extent, if atall, even when left standing for a considerable length of time, andwhich, if settled, readily may be dispersed by stirring. Example 4.-500parts of a 42 per cent. presscake of Alizarine NAC, prepared by thefiltration sulting press-cake is then agitated with 24 parts of thediethyleizieglycol-wa .ter mixture and about 1 part of ammoniumhydroxide solution until a fluid paste is produced. The resulting paste,which contains about 40 percent. of the dyestuif, when spread in a thinlayer on a glass plate and exposed to, the atmosphere for several weeks,

shows no indication of drying; and when subsequently added to water withagitation, as in the preparation of a dye-bath, readily dispersesthroughout the bath.

It will be realized that the invention is no limited to the products orto the process and the details thereof which are set forth in theforegoing example. Thus, the process may be, ap-. plied to thepreparation of highly concentrated filter-cakes and/or pastes of other,preferably metal-free anthraquinone compounds, more particularly otherhydroxyanthraquinones, and es-, pecially other dihydroxyanthraquinonesand socalled alizarine dyestuffs"; as for example, 1.2.4-trihydroxyanthraquinone,- 1.2-dihydroxy-3-nitro-anthraquinone,1.5-dihydroxyanthraquinone, 1.8-dihydroxyanthraquinone,1.4-dihydroxyanth r a q ui n o n e, 1.2.7-trihydroxyanthraquinone,1.2.G-trihydroxyanthraquinone, 1.2.5.8-tetrahydroxyanthraquinone,indanthrone, flavanthrone,

dibenzanthrone, chlorindanthrone, chlorquinizarine'; etc.

The concentrated filter-cakes or equivalent masses produced inaccordance with the invention may. be employed for the production ofproducts other. than concentrated suspensions orpastes; for example,they maybe dried by heat-- ing under vacuum to produce powders, etc.

' The amount of water used informing the slurry from the concentratedfilter-cake or equivalent mass may vary over a wide range. The minimumamount being that required to form with a filtercake or mass beingtreated a slurry which is capable 'of agitatiom. Frequently none need beadded, as in Eaxmple 1.

It will be furthermore understood that inf' stead of producingdispersion by stirring, as-de forms of agitation may be em? suction,pressure, centrifugal, and other types 01 fllters, as well as variousother methods 01 separating suspended solids from liquids, p ierabivmechanical, may be employed. I v

The expression -metal-free anthraquinone compound, as employed aboveandin the claims,

denotes and includes the anthraquinone compounds which are free frommetallic substituents;- for example, alizarine, as. dlsl-l d fl hed fromits calcium salt.

Since changes maybe made in carrying out the above process and in theproductsand ingredients and proportions thereof without departing iromthe scope oi the invention, it is intended that all matter contained inthe above description shall be interpreted as illustrative small amountof acolloiding agent in the .torm.

01' a fluid paste which is relatively non-drying.

2. A composition of matter consisting of a liquid suspension of ananthraquinone compound,

containing more than 30 per cent. by weight of said compound, and asmall amount of a protective colloid as a stabilizing agent, in the formof a fluid paste.

.3. A composition 0! matter consisting of a liquidsuspension oi ahydroxyanthraquinone compound, containing more than 30 per cent. by

we$ht of said-compound, a high-boiling, inert,

organic liquid hygroscopic substance, and a small amounts! acolloidingagent in the form ot a fluid paste which is relatively non-drying anddoes .not'sjettle to any considerable extent on ,4.-A composition'oimatter consisting oi aqueous-suspension a hydroxyanthraquinone compound,containing not less than 40 per cent. by weight of said compound, ahigh-boiling, inert,

' organic liquid hygroscopic substance, and a'small v colloidins agent,in the form or a fluid pasteyrhich is relatively non-dryi s.

A tion or matter consistingo! an suspension or alizarine containing notaqueous lemthanao per cent.b'yweightot alimrine-and a at afluid pastewhiclrdoes not settle small amount of a-colloiding agent, in the form toany considerable extent on-standing. I

6. A composition or matter consisting of an aqueous suspension ofalizarine containing not less than 40 per cent. by weight of saidalizarine, sulflte cellulose waste liquor in an amount not exceeding 2per cent. of the weight of the slimrine, and diethylene glycol.

'l. A process of preparing a concentrated suspension of an insolubleantraquinone compound from a less concentrated paste thereof from whichliquid-is not removable merely by flltration, which comprises agitatingsaid paste without addition of liquid, to liberate liquid and form afluid suspension of said compound, mechanically separating liquid fromthe fluid suspension, and agitating the resulting separated compound, toform a fluid suspension.

- 8.A process of preparing a concentrated suspension of an insolubleanthraquinone compound, which comprises agitating a liquid-containingmat of said with a small amount or 2,000,720 ployed; and that. varioustypes of fllters, such as an alkaline material and a small amount of acolloiding agent as dispersing agents, to iorm a thin, fluid suspensionof said compound, mechanically separating liquid from the fluidsuspension, to form a thick liquid-containing mass 0! said compound, andagitating the. resulting thick mass to form a thin, fluid suspension.

9. A process or preparing a concentrated aqueoussuspension of ananthraquinone compound from a filter-cake of said compound, obtained byfllte'ring a suspension in dilute acid or said compound, which comprisesstirring said filter-cake with a small amount or an alkaline materialand a small amount of an alkylnaphthalene-iormaldehyde-suliuric acidcondensation product as dispersing agents, to form a thin, fluidsuspension of said compound, separating liquid from the suspension, toform a thick liquid-containing mass of said compound, and stirring theresulting thick mass with an additional small amount or dispersingagent, to form a thin, fluid suspension.

10. In a prooess'oi preparing a concentrated paste 0! aninsolubleanthraquinone compound, the improvement which comprisesagitating a liquid-containing mass or said compound in the form of apaste from whi'chliquid is not removable merely by filtration, toliberateliquid and form a fluid suspension of said compound, and

mechanically separating liquid from the fluid suspension.

11. In a process of preparing a concentrated suspension of an insolubleanthraquinone compound, the improvement which comprises agitating aliquid-containing 'mass of said compound with a dispersing agent capableof reducing the viscosity of said mass without substantially decreasingthe concentration of said compound in said mass, to form a fluidsuspension or said com-.

pound, and mechanically separating liquid from the fluid suspension.

12. A process of preparing ,a concentrated.

aqueous suspension of a hydroxyanthraquinone compound from a filter-cakeof said compound, obtained by flltering an aqueous suspension of saidcompound, which comprises stirring saidfilter-cake, to liberate water"and a fluid suspension of said compound, mechanically separatingliberated water trom the fluidsuspensiori, and

stirring the-resulting mass of said compound, to

form a fluid suspension.

, 13. A process of preparing a concentrated suspension of ahydroxyanthraquinone compound from a filter-cake of said compoundcontaining water, which comprises stirring said fllter -cake with asmallv amount of an alkaline material as adispersing agent, to form' athin fluid suspension of said compound, separating the suspendedcompoundcontaining' water from the fluid suspension, to form a thick,liquid-containing mass, and stirring the resulting mass,'to form a thin,fluid suspension.

14. A process of preparing a concentrated suspension ot ahydroxyanthraquinone compound from a filter-cake of said compound, whichcomprises agitating said fllter-cake with a small amount of a dispersingagent capable .of reducins the viscosity of said filter-cake, to form afluid suspension of said compound, mechanically separating liquid fromthe fluid suspension to iorm a thick liquid-containing mass, agitatingthe resulting mass with an additional small amoimt oi dispersing agent,to form a thin, fluid suspension, and incorporating into said suspensiona small amount of a protective colloid, as a stabiliaing agent.

obtained by filtering a suspension 'indilute acid oi'said compound,which comprises stirring said --fllter-cake with a small amount or adispersing agent capable of reducing the viscosity of said filter-cakewithout substantially decreasing the concentrationof said compound insaid filtercake, to form a "fluid suspension or said compound,mechanically separating water from the suspension to form a thick masscontaining water, stirring the'resulting mass with an additional .smallamount of dispersing agent to form a thin, fluid suspension, andincorporating into said suspension a small amount of a protectivecolloid, as a stabilizing agent, and a hygroscgpic substance.

16. A process of preparing 'a concentrated aqueous suspension of a'dihydroxyantliraquinone from a filter-cake of saiddihydroxyanthraquinone, which comprises stirring said filter-cake with asmall amount ot-an alkaline material as a dispersing agent, to form athin, fluid suspension of said dihydroxyanthraquinone,-flltering oil thedihydroxyanthraqi'iinone, and stirring the 'resulting filterecake? withan additional smallamount of dispersing agent, to form a thin, fluidsuspension. we 1 17. A process of preparing a concentrated aqueoussuspension of a dihydroxyanthraquinone from a'filter-cake of saiddihydroxyanthraquin ,one, which comprises stirring said filter-cake withasmall amount'oi an alkalinematerial as a dispersing agent, to form athin, fluid suspension of said dihydroxyanthraquinone, filtering oil!the dihydroxyanthraquinone, stirring the re-'- sulting filter-cake with.an; additional small amount of alkali, as a dispersing agent, to iorm athin, fluid suspension, and incorporating into said suspension ahigh-boiling, inert, organic liquid hygroscopic substance.

18. A process of preparing a concentrated aqueous suspension ofalizarine from a filtercake of alizarine, obtained by filtering asuspension in dilute acid of said alizarine, which comprises stirringsaid filter-cake with a small amount of an alkanol amine as a dispersingagent, to form a thin, fluid suspension of said alizarine, filtering oifthe alizarine, and stir.-

ring the resulting filter-cake with an additional,

l9. A process of preparing a concentrated aqueous suspension ofalizarine from a filter-cake oi! alizarine, obtained by filtering asuspension in dilute acid of said alizarine, which comprises stirringsaid filter-cake with a small amount of ammonium hydroxide as adispersing agent, to form a thin, fluid suspension of said alizarine,filtering oif the alizarine, stirring the resulting filter-cake withanadditional small amount of alkali as a dispersing agent, to form a thin,fluid suspension, and-incorporating into said suspension a smallamountof neutralized sulflte cellulose waste liquor, as a stabilizing agent. 7

otsodium hydroxide as a dispersing agent, to

form a thin, fluid suspension of said alizarine,

filtering oil the alizarine, replacing a portion of-the water in the,filter-cake with diethyleneglycoLand stirring the resulting filter-cakewith .a small amount of sodium hydroxide as a dispersing agent, to forma thin, fluid, suspension which does not dry out on exposure to theatmosphere. a v I 21. In a process of preparing a concentrated aqueoussuspension of alizarinefrom a filter-cake of alizarine, obtained byfiltering asuspension .in dilute acid of said alizarine, the improvementwhich comprises stirring said filter-cake with a small amount of sodiumhydroxide as a dispersing agent, to form a thin, fluid suspension ofsaid alizarine, and filtering off the alizarine.

22. In a process of. preparing a concentrated paste 0! an anthraquinonecompound, the improvement which comprises incorporating a mass of saidcompound with a dispersing agent capable of reducing the viscositythereof without substantially decreasing the concentration of saidcompound in said mass,.to form a fluid suspen-- amount of an alkalinematerial as a dispersing agent, to form a thin; fluidsuspensi'on of saiddihydroxyanthraquinone, and filtering oi! the .dihydroxyanthraquinone. I

24. An aqueous fluid paste 01 a dibydr'oxyanthraquinone containing about40 to about' 75 per cent. by weight of dihydroxyanthraquinone, ap-

proximately 60 to approximately 25 per cent. 02'

water and not more than about 2 per cent. of a colloiding agent.

25. 'A composition of matter consisting of an aqueous suspension ofalizarine containing 'not less than 40 per cent by weight of alizarine,direthylene glycol, and a colloiding agent inan' amount not exceeding 2per cent of the weight of alizarine.

26. A process of preparing a concentrated aqueous suspension of adihydroxyanthraquinone from a filter-cake of saiddihydroxyanthraquinone, which comprises agitating said filter-cake witha dispersing agent capable of reducing the viscosity of said filter-cakewithout substantially decreasing the concentration of saiddihydroxyanthraquinone therein,'to form a fluid suspension of saiddihydroxyanthraquinone, filtering off the dihydroxyanthraqinone, andagitating the resultingfllter-cake in the presence of said dis-' a fluidsuspension.

persing agent to form I DONALD G. ROGERS.

cnnmloxm or commotion. Patent Nd. 2,0 6,126.; l uJnly 1935. I DONALD G.ROGERS. 4 l ltis herehy certified that error appears in the printed specification'oi. the above numbered patent requiring correction asfollows: Page 4; first column,

line 70, claim 7, strike out the words and comma 'resulting separatedcompound." and insert the words remaining mass; second-column, line. 46,claim 12. after "and" insert form; line 57, claim 13, before"separating? insert mechanically;

and lines 57 and 58, same claim, strike outthe words "the suspendedcompound "containing"; and that the said Letters Patent should be readwith-these corrections therein that the same may conform to the recordof the case in the Patent Office.

Signed and sealed this 20th day of August, A. D. 1935.

Leslie Frazer (Seal) 7 i .Acting couuuissioner of Patents.

